Popovich A. Formation of residual stresses in parts' surface layers depending on the surface plastic deformation parameters

The research object is process of strengthening by means of surface plastic deformation. The research subject is residual stress in parts after surface plastic deformation, influence of the surface plastic deformation parameters on fatigue life of strengthened specimens. Aim of the research is formation of compressive residual stress with rational through-depth distribution in surface layers of strengthened parts by means of surface plastic deformation parameters enhancement. Methods of the research are as follows. Determination of the force pressing an instrument to the part by which a transition from elastic deformation to elasto-plastic deformation begin is made on the basis of Hertz - Belyayev contact problem theory. Comparison of the residual stress dependences on depth which is measured off the part surface is done on the basis of dimensional theory. Statements of elasto-plastic contact deformation problems are done on the basis of plastic flow theory. Modeling of the elasto-plastic deformation process is carried out using the finite element method. Maximal force of the elastic wire action on the part surface during impact time is determined using the energy balance method. Fatigue life testing of axially symmetrical and plane specimens is carried out using the standard techniques. Experimental results were treated using the mathematical statistics methods. The results attained are as follows. The useful ratio between deforming forces and the feed ratio at preliminary and final passes of surface plastic deformation with hardening elements of different sizes are obtained. It is established surface plastic deformation schemes, which allow creating of more rational residual compressive stresses distribution in parts' surface layers. Higher strengthening effect of deformation according to above mentioned schemes is proved. Treatment schemes, which were proposed in the thesis, are recommended to use for strengthening of gas turbine engine parts and internal combustion engine parts. Introduced at Motor Sich JSC. Area of application is mechanical engineering.